The 5 Parsecs / Chain Reaction 2015 Hack

After several games of 5 Parsecs from Home (5P), I realised that the enemy AI -- while viable -- was still a bit basic. I needed to up the stakes to get a decent challenge. One way, of course, is to simply increase the number of opponents above the recommended method of determining them. One downside to this of course, is that I'd need more minis... which I'd then have to buy, especially if I wanted to keep playing the game in 15mm.

Another method is to determine an objective combined with a time limit which would then give me a win/loss method without having to search for more complicated solutions.

The third and final method is to replace the existing enemy AI rules with another set... equally rules light but would give a bit more challenge.

I recently tried some games of Two Hour Wargames' Chain Reaction (CR) rules. Specifically the free 2015 edition as that seemed the best of all the variants available.

I played 2 sessions, trying to find the best balance and way of merging the 5P character stats (there are about 3 that are relevant: Move, Combat, Armour) with the CR stat... only one, which is REP(utation).

The best way (for me) was to add the Rep to the existing statline, replacing Agility. That allowed me to also add uncertainty to the activation sequence, with the added rule of ALL modls would get to activate... just some would be last on the list. that could be an advantage or disadvantage, depending on the situation.

I used the 5P Move stat (average of 4") to enable me to continue playing on a 2x2 instead of the CR move stat of 8" which meant I'd have to play on a 3x3.

The 5P Combat stat... I've been trying out giving either a +1d6 to the combat rolls or a +1 to the combat roll, depending on the Combat stat. Doing the former gave better odds of success, although it's still dependent on the RNG deities. Doing the latter gave a more predictable hit result. Given that I'd normally need a 6+ to hit something whichever rule set I used, simply due to the fact that most times the minis will be in cover. Both methods are viable ones, although I'm tending to give a straight +1 bonus (for every 2 5P Combat stat) simply due to the fact that both rule sets allow you to split fire between different targets and giving a +1d6 bonus die would complicate things. Which roll do I give the bonus die? I also kept the weapon ranges and use the 5P "Shots" as equal to the CR "Target" stat. That meant most models were rolling only 1 die as they fired... which is same as 5P. I used the CR ranged combat table.

I'll probably not use the 5P Toughness Stat, as the CR method of rolling on the Rep does almost the same thing. The only change I made was giving a +1 bonus to Rep when rolling for damage to account for combat armour. So a character with Rep 4 (the standard Rep for my characters aside from the Leader) will use a Rep 5 when rolling for Combat Damage, but rep 4 for everything else.

I used Savvy as per 5P to try and Seize the Initative.

I also used the basic CR 2015 Reaction rules for my crew.

I didn't use the Star Power or any of the Star bonuses from CR.

For the enemy... same rationale for stat lines.

Since I also own 5150 Star Army (both editions) and Citizen Soldier, I hacked the Reaction tests to reflect the type of enemy, as 5150 gave different enemy types some Different Reaction test results. 

In my latest game (a Patron mission, Secure, vs. a hulker gang) I gave the hulkers the Grath Reaction Test tables. Worked well. They even had a bonus for melee combat as per the 5P rules.

For enemy AI movement and activations, Star Army gives the AI 3 basic "stances": Attack, Defend or Patrol. Worked well also, but I would add "movement to objective and shoot if possible" when on an Attack stance as per the mission.

What I liked about using the CR rules is the addition of PEFs (Possible Enemy Forces). Placing 3 PEFs on the table (per the CR setup rules) ensured that I was never sure WHERE the enemy would pop up.

In actual game play, things worked out pretty well. I had three PEFs numbered 1, 2 and 3. Whenever a PEF came into LOS, I'd flip the counter over. A "1" meant that was the actual enemy force. A "2" or "3" was a false alarm. Of course, the tension is lessened when the first PEF flipped over is a "1" but them's the breaks.

Also, even though my characters would activate, I wasn't able to fully control them thanks to the Reaction and In Sight Tests. Sometimes, my characters would move out to shoot, only to have the enemy win the test and shoot at me, and I'd have to duck back into cover again. Other times, the enemy would shoot at me, miss and I get to shoot back and we'd trade fire back and forth a few times before they ducked back into cover or dropped dead or out of action. I've taken a shot at an AI enemy, sending it scurrying back to cover... only to have it cross the LOS of another of my models... who won the In Sight test and shot the AI enemy down! All these worked well to add some uncertainty to my activations. 

Even the "Man Down" reaction test worked well, as that was compatible with the 5P morale test. The only thing is, once they are less than 50% strength is when they HAVE to pass the test on one die or else run away. I think for the hulker gang, I should've given them 3 dice to start with so they would be rolling on 2 dice even with the -1d6 penalty for taking 50%+ losses. That would jive better with the "fail morale only on a roll of 1" that is in the 5P rules.

I did give them 3 dice for enemy activations and movement, taking the best of 2 results since they were so aggressive. 

Overall, my experience was pretty positive although the mission objective of the enemy needing to occupy the facility and me fending them off meant I could get into a defensive position and stand off, relying on Reaction Tests to down the enemy, as the non-moving side would win draws. Korg was the star here, with his 4d6 rate of fire. That meant that if the hulkers didn't go down after being shot at with 4 dice (usually, yes) they would Duck Back into cover as they were Outgunned.

The reason, I think, why CR rules hack worked, was that the 2 games shared some common DNA:

- semi-random activations, with player and AI enemy activations all mixed up 

- ranged combat using very similar weapons stats

- morale checks to see if the factions will leave the battle or not

Overall, I think I could even tweak the tables to reflect each crew member (if I so desired) to reflect their capabilities, and maybe add a bonus or two to the enemy to make things tougher on myself. 

VERDICT: I'll keep on using and tweaking the CR 2015 rules for 5P as it makes for a more interesting and challenging game without too much extra overhead in terms of complexity (once I've finalised all the tables and charts that is). 

Of course, I'm still using the rest of the 5P rules to play the campaign, as that's so much easier to do than using the full 5150 Citizen Soldier or Star Army rules, and there's more story to be had in the 5P tables.


  1. This is interesting since I also prefer the THW combat rules for the solo AI, simplicity and quick resolution. Did you use the 5P weapons or the THW weapons?

  2. That's a good question. I think I mapped the 5P weapons to the THW ones.


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